Word Search in Trie in DSA Go - Execution Trace

Concept Flow - Word Search in Trie

Start at root node

↓

For each letter in word

↓

Check if letter child exists?

No→Word NOT found

Yes↓

Move to child node

↓

Repeat for next letter

↓

After last letter, check isWord flag

↓

If isWord true -> Word FOUND

↓

Else -> Word NOT found

Start from the root and check each letter of the word in the trie nodes. If all letters exist and the last node marks a word end, the word is found.

Execution Sample

DSA Go

func Search(root *TrieNode, word string) bool {
    node := root
    for _, ch := range word {
        if node.children[ch-'a'] == nil {
            return false
        }
        node = node.children[ch-'a']
    }
    return node.isWord
}

This code searches for a word in a trie by traversing nodes for each letter and checking if the final node marks a complete word.

Execution Table

Step	Operation	Current Letter	Node Children Check	Move Pointer	Visual State
1	Start at root	-	Root has child 'c' for 'c'?	Move to child 'c'	root -> c
2	Check letter 'a'	a	Node 'c' has child 'a'?	Move to child 'a'	root -> c -> a
3	Check letter 't'	t	Node 'a' has child 't'?	Move to child 't'	root -> c -> a -> t
4	End of word	-	Node 't' isWord?	No move	root -> c -> a -> t (isWord=true)
5	Result	-	-	-	Word FOUND

💡 Traversal ends after last letter; isWord flag true means word found.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
node	root	node at 'c'	node at 'a'	node at 't'	node at 't'	node at 't'
current letter	-	c	a	t	-	-

Key Moments - 3 Insights

Why do we check if the child node exists before moving?

Because if the child node for the current letter does not exist (see execution_table step 2), the word cannot be in the trie, so we stop searching.

Why do we check the isWord flag at the last node?

Because the path may exist but not represent a complete word. Only if isWord is true (execution_table step 4) do we confirm the word is stored.

What happens if the word is empty?

The loop does not run, so we check if root.isWord is true. Usually root.isWord is false, so empty word is not found.

Visual Quiz - 3 Questions

Look at the execution_table, what is the node pointer after checking letter 'a'?

A Node at 't'

B Node at 'c'

C Node at 'a'

D Root node

💡 Hint

Check the 'Move Pointer' column at step 2 in execution_table.

At which step does the search confirm the word is found?

A Step 3

B Step 5

C Step 2

D Step 4

💡 Hint

Look at the 'Result' row in execution_table where word FOUND is stated.

If the node for letter 't' was missing, what would happen?

A Search returns false at step 3

B Search continues to next letter

C Search returns true

D Search checks isWord flag

💡 Hint

Refer to 'Node Children Check' and 'Operation' columns in execution_table step 3.

Concept Snapshot

Word Search in Trie:
- Start at root node
- For each letter, check if child node exists
- Move pointer to child node if exists
- After last letter, check isWord flag
- If true, word found; else not found

Full Transcript

To search a word in a trie, start at the root node. For each letter in the word, check if the current node has a child node for that letter. If not, the word is not in the trie. If yes, move to that child node and continue. After processing all letters, check if the last node marks the end of a word (isWord flag). If it does, the word is found; otherwise, it is not. This process ensures only complete words stored in the trie are recognized.